The present invention relates to an intermediate conveying apparatus that superposes plural sheets conveyed from an image forming apparatus and conveys the superposed sheets to a subsequent post-processing apparatus while the plural sheets are superposed.
In recent years, an image forming apparatus of an electrophotographic type has been used in a field of quick printing. Further, bookbinding printing of a print-on-demand type “for printing copies in necessary quantity only when needed” is made possible by using an image forming apparatus equipped with a post-processing apparatus that conducts various types of post-processing operations.
In addition, efficiency improvement of bookbinding operations and cost reduction are greatly expected, because no preparation of a printing plate is needed.
The image forming system disclosed in Japanese Patent Publication Open to Public Inspection No. 2005-15225 represents an apparatus wherein the aforesaid demands are satisfied, and it is an image forming system wherein a single sheet processor that is a type of a post-processing apparatus is connected on the sheet ejection side of an image forming apparatus, and at least one type of post-processing apparatus out of plural types of post-processing apparatuses is further connected to the single sheet processor.
Further, in the image forming apparatus and in the image forming system wherein a post-processing apparatus is connected to the image forming apparatus, it is demanded that the number of processed sheets per unit of time (hereinafter referred to as productivity) is large. In the field of quick printing, in particular, that demand is strong. And in many cases, the number of processed sheets in the image forming system is determined by a capacity of the post-processing apparatus rather than that of the image forming apparatus.
Namely, in the post-processing apparatus, it is necessary to secure a sufficient distance of an interval between successive sheets (hereinafter referred to as a sheet interval), because there are many cases where conveyance of sheets is temporarily stopped for processing. As measures for that purpose, a conveyance speed in the post-processing apparatus is increased to be higher than that in the image forming apparatus. However, a speed increase for the conveyance speed in the post-processing apparatus is close to the limit, because the conveyance speed for the image forming apparatus has been raised due an attempt of speeding up in recent years.
With the foregoing as a background, each of Japanese Patent Publication Open to Public Inspection Nos. 10-250914, 2003-2503 and 2003-54809 discloses an apparatus wherein an intermediate storing section that stacks plural sheets in an image forming apparatus or in a subsequent post-processing apparatus is provided, and plural sheets stacked on an stacking section are conveyed together simultaneously. By conveying these plural superposed sheets simultaneously like this, it is possible to broaden sheet intervals by an equivalent of the superposed sheets without increasing the conveyance speed, namely, it is possible to improve productivity in the post-processing apparatus.
However, in the case of the apparatus described in Japanese Patent Publication Open to Public Inspection No. 10-250914 or in Japanese Patent Publication Open to Public Inspection No. 2003-54809, it is necessary to provide an intermediate storing section on each of post-processing apparatuses when connecting plural types of post-processing apparatuses as in Japanese Patent Publication. Open to Public Inspection No. 2005-15225, because an intermediate storing section is provided in the post-processing apparatus.
In the apparatus described in Japanese Patent Publication Open to Public Inspection No. 2003-2503, an unnecessary apparatus is provided when using an image forming apparatus without connecting the post-processing apparatus, because an intermediate storing section is provided in the image forming apparatus.